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5.3.3A  Discovery Request - Model B procedures |R13|Word‑p. 71

5.3.3A.1  General

The Discovery Request is sent by the Discoveree UE or the Discoverer UE in order to be authorised to access the discovery resources and perform restricted ProSe Direct Discovery, Model B.

5.3.3A.2  Discoveree Request (non-roaming) - restricted discovery

(not reproduced yet)
Figure 5.3.3A.2A-1: Discoveree UE procedures for Model B restricted discovery (non-roaming)
Up
Step 0.
The user sets the permission for the restricted discovery using application layer mechanisms. In addition, the application client in the UE retrieves its own PDUID and provides it to the ProSe Application Server. The ProSe Application Server allocates a Restricted ProSe Application User ID (RPAUID) for that PDUID, stores the binding between the PDUID and the RPAUID and returns the RPAUID to the application client in the UE. The UE may optionally provide metadata to be associated with the RPAUID, and the ProSe Application Server stores the metadata. The application client in the UE stores the binding between the PDUID and its own RPAUID. When the application client in the UE intends to use the ProSe service, it triggers the UE to perform a Discoveree request procedure providing its own RPAUID obtained from the ProSe Application Server.
Step 1.
If the Discoveree UE is authorised to use Model B discovery in the serving PLMN, or if UE intends to use Model B discovery using WLAN-based PC5 and is triggered by the application client to perform a Discoveree Request procedure, the UE shall establish a secure connection to the ProSe Function in the HPLMN and send a Discovery Request (RPAUID, UE Identity, command, Discovery Type, Discovery Model, Application ID, Discovery Entry ID, [PC5_tech]) message. The RPAUID indicates what the UE is interested to announce. The UE Identity is set to IMSI. The command indicates that this is for ProSe Response operation, i.e. for a Discoveree UE. The Discovery Type is set to "restricted discovery" and the Discovery Model indicates "Model B". The Application ID represents a unique identifier of the UE application that has triggered the transmission of the Discovery Request message. The Discovery Entry ID indicates whether this is a new request. PC5_tech is an optional parameter that indicates the PC5 radio technology (e.g. E-UTRA, WLAN) that UE wishes to use for Model B discovery. PC5_tech may include more than one PC5 radio technology. When this parameter is omitted the intended PC5 radio technology is E-UTRA. This request is always sent to the ProSe Function in HPLMN.
Step 2.
The ProSe Function checks for the authorization of the application represented by the Application ID. If there is no associated UE context, the ProSe Function shall check with HSS the authorisation for discovery and, if necessary, create a new context for this UE that contains the subscription parameters for this UE. The HSS provides the MSISDN of the UE. The HSS also provides the serving PLMN ID of where the UE is registered. When the Discovery Entry ID in the Discovery Request message does not contain a valid value for this UE, the ProSe Function creates a new discovery entry in the UE's context for this request, and returns the corresponding identifier in the Discovery Response message in step 5.
Step 3.a.
Optionally, the ProSe Function sends an Auth Request (RPAUID, Request Type) to the ProSe Application Server. The ProSe Function locates the ProSe Application Server based on the Application ID. The Request Type is set to "restricted discovery/response".
Step 3.b.
The ProSe Application Server returns an Auth Response (PDUID(s), Response Type) message. The PDUID(s) corresponds to the RPAUID stored in the ProSe Application Server. The Response Type is set to "restricted discovery/response ack". The ProSe Function verifies that at least one of the received PDUID(s) belongs to the requesting UE.
Step 4.
The ProSe Function in the HPLMN allocates a ProSe Response Code, a ProSe Query Code, and an associated Discovery Query Filter(s). The ProSe Function also allocates a validity timer that is associated to the ProSe Response Code. The ProSe Response Code corresponds to the RPAUID that was contained in the Discovery Request from the UE. The validity timer shall indicate for how long this ProSe Response Code is going to be valid. The UE will be authorised to respond with this ProSe Response Code for the duration of validity timer and if it remains in the same PLMN. The ProSe Function stores the RPAUID, the ProSe Response Code, the ProSe Query Code and Discovery Query Filter(s), and the associated validity timer in the user context.
Step 5.
The ProSe Function in HPLMN shall respond with a Discovery Response (Discovery Model, ProSe Response Code, Discovery Query Filter(s), validity timer, Discovery Entry ID, [PC5_tech]) message. The Discovery Model indicates that Model B is used. Multiple Discovery Query Filters may be returned. The Discovery Query Filter provides means for the Discoveree UE to determine if a received ProSe Query Code should trigger an announcement of the assigned ProSe Response Code. The ProSe Response Code is provided by the ProSe Function and corresponds to the RPAUID that was contained in the Discovery Request. The validity timer indicates for how long this ProSe Response Code and associated Discovery Query Filter(s) is going to be valid. When the validity timer expires or the UE changes its registered PLMN, the UE needs to initiate a new Discoveree Request procedure. The optional PC5_tech parameter indicates the PC5 radio technology(ies) that is/are authorized to be used for the assigned ProSe Response Code. When this parameter is omitted, the authorized PC5 radio technology is E-UTRA.
Step 6.
The UE may then obtain the radio resources to monitor using the Discovery Query Filter(s), as authorised and configured by E-UTRAN for ProSe as defined in RAN specifications, or uses WLAN or both.
If the validity timer associated with a ProSe Response Code expires (because the UE has not refreshed the corresponding Discovery Request within the duration of the validity timer), then the ProSe Function removes the entry related to that ProSe Response Code from the UE context.
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5.3.3A.3  Discoveree Request (roaming/inter-PLMN transmission) - restricted discoveryWord‑p. 73
(not reproduced yet)
Figure 5.3.3A.3A-1: Discoveree UE procedures for Model B restricted discovery (roaming)
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The UE is only allowed to announce in the carrier frequency signalled from serving PLMN. When inter-PLMN discovery transmission is supported, the carrier frequency may be operated by Local PLMN.
Step 0.
The user sets the permission for the restricted discovery using application layer mechanisms. In addition, the application client in the UE retrieves its own PDUID and provides it to the ProSe Application Server. The ProSe Application Server allocates a Restricted ProSe Application User ID (RPAUID) for that PDUID, stores the binding between the PDUID and the RPAUID and returns the RPAUID to the application client in the UE. The UE may optionally provide metadata to be associated with the RPAUID, and the ProSe Application Server stores the metadata. The application client in the UE stores the binding between the PDUID and its own RPAUID. When the application client in the UE intends to use the ProSe service, it triggers the UE to perform a Discoveree request procedure providing its own RPAUID obtained from the ProSe Application Server.
Step 1.
If the Discoveree UE is authorised to use Model B discovery in the PLMN operating the carrier frequency signalled from the serving PLMN (VPLMN or Local PLMN), or if UE intends to use Model B discovery using WLAN-based PC5 and is triggered by the application client to perform a Discoveree Request procedure, the UE shall establish a secure connection to the ProSe Function in the HPLMN and send a Discovery Request (RPAUID, UE Identity, command, Discovery Type, Discovery Model, Application ID, Discovery Entry ID, [Announcing PLMN ID], [PC5_tech]) message. The RPAUID indicates what the UE is interested to announce. The UE Identity is set to IMSI. The command indicates that this is for ProSe Response operation, i.e. for a Discoveree UE. The Discovery Type is set to "restricted discovery" and the Discovery Model indicates "Model B". The Application ID represents a unique identifier of the UE application that has triggered the transmission of the Discovery Request message. The Discovery Entry ID indicates whether this is a new request. If inter-PLMN ProSe discovery transmission is supported, and the serving PLMN signalled carrier frequency is not operated by HPLMN or VPLMN, the UE shall include the PLMN ID of that carrier frequency in the Announcing PLMN ID. PC5_tech is an optional parameter that indicates the PC5 radio technology (e.g. E-UTRA, WLAN) that UE wishes to use for Model B discovery. PC5_tech may include more than one PC5 radio technology. When this parameter is omitted the intended PC5 radio technology is E-UTRA. This request is always sent to the ProSe Function in HPLMN.
Step 2.
The ProSe Function checks for the authorization of the application represented by the Application ID. If there is no associated UE context, the ProSe Function shall check with HSS the authorisation for discovery and, if necessary, create a new context for this UE that contains the subscription parameters for this UE. The HSS provides the MSISDN of the UE. The HSS also provides the serving PLMN ID of where the UE is registered. When the Discovery Entry ID in the Discovery Request message does not contain a valid value for this UE, the ProSe Function creates a new discovery entry in the UE's context for this request, and returns the corresponding identifier in the Discovery Response message in step 7.
Step 3.a.
Optionally, the ProSe Function sends an Auth Request (RPAUID, Request Type) to the ProSe Application Server. The ProSe Function locates the ProSe Application Server based on the Application ID. The Request Type is set to "restricted discovery/response".
Step 3.b.
The ProSe Application Server returns an Auth Response (PDUID(s), Response Type) message. The PDUID(s) corresponds to the RPAUID stored in the ProSe Application Server. The Response Type is set to "restricted discovery/response ack". The ProSe Function verifies that at least one of the received PDUID(s) belongs to the requesting UE.
Step 4.
The ProSe Function in the HPLMN allocates a ProSe Response Code, a ProSe Query Code, and an associated Discovery Query Filter(s). The ProSe Function also allocates a validity timer that is associated to the ProSe Response Code. The ProSe Response Code corresponds to the RPAUID that was contained in the Discovery Request from the UE. The validity timer shall indicate for how long this ProSe Response Code is going to be valid. The UE will be authorised to respond with this ProSe Response Code for the duration of validity timer and if it remains in the same PLMN. The ProSe Function stores the RPAUID, the ProSe Response Code, the ProSe Query Code, and Discovery Query Filter(s), and the associated validity timer in the user context.
Step 5.
If the Discovery Request is authorised then the ProSe Function in the HPLMN shall inform the ProSe Function in VPLMN or Local PLMN with the Announce Authorisation (Restricted ProSe Application User ID, Application ID, ProSe Response Code, validity timer, UE Identity, Discovery Entry ID, [PC5_tech]) message. The Restricted ProSe Application User ID corresponds to the request from the UE, whereas the ProSe Response Code indicates the assigned code for this request. The request also includes the UE identity information e.g. IMSI or MSISDN in order to allow the ProSe Function in VPLMN or Local PLMN to perform charging. The validity timer indicates for how long this ProSe Response Code is going to be valid. If the ProSe Function in VPLMN or Local PLMN receives the same Discovery Entry ID in a subsequent Announce Authorization message, it updates the discoveree UE's corresponding discovery entry replacing the existing ProSe Response Code and validity timer with the last received ones. The request may also include the PC5_tech parameter if it was provided by the UE in step 1. When this parameter is omitted the intended PC5 radio technology is E-UTRA.
Step 6.
The ProSe Function in VPLMN or Local PLMN authorizes the UE to perform ProSe Direct Discovery announcing.
Step 7.
The ProSe Function in HPLMN shall respond with a Discovery Response (Discovery Model, ProSe Response Code, Discovery Query Filter(s), validity timer, Discovery Entry ID, [PC5_tech]) message. The Discovery Model indicates that Model B is used. Multiple Discovery Query Filters may be returned. The Discovery Query Filter provides means for the Discoveree UE to determine if a received ProSe Query Code should trigger an announcement of the assigned ProSe Response Code. The ProSe Response Code is provided by the ProSe Function and corresponds to the Restricted ProSe Application User ID that was contained in the Discovery Request. The validity timer indicates for how long this ProSe Response Code and associated Discovery Query Filter(s) is going to be valid. When the validity timer expires or the UE changes its registered PLMN, the UE needs to UE needs to initiate a new Discoveree Request procedure. The optional PC5_tech parameter indicates the PC5 radio technology(ies) that is/are authorized to be used for the assigned ProSe Response Code. When this parameter is omitted, the authorized PC5 radio technology is E-UTRA.
Step 8.
The UE may then obtain the radio resources to monitor using the Discovery Query Filter, as authorised and configured by E-UTRAN for ProSe as defined in RAN specifications, or uses WLAN or both.
If the validity timer associated with a ProSe Response Code expires (because the UE has not refreshed the corresponding Discovery Request within the duration of the validity timer), then the ProSe Function removes the entry related to that ProSe Response Code from the UE context.
Up

5.3.3A.4  Discoverer Request (non-roaming) - restricted discoveryWord‑p. 75
(not reproduced yet)
Figure 5.3.3A.4A-1: Discoverer UE procedures for Model B restricted discovery (non-roaming)
Up
Step 0.
In this step, the application client in the UE retrieves its own PDUID and provides it to the ProSe Application Server. The ProSe Application Server allocates a Restricted ProSe Application User ID (RPAUID) for that PDUID, stores the binding between the PDUID and the RPAUID and returns the RPAUID to the application client in the UE. The application client in the UE stores the binding between the PDUID and its own RPAUID, obtains the RPAUID of those users (Target RPAUIDs) from the ProSe Application Server and triggers the UE to perform the ProSe query procedure, providing its own RPAUID and the Target RPAUIDs. The Target RPAUIDs of the UEs to be queried are passed in an Application Level Container.
Step 1.
If the Discoverer UE is authorised to use Model B discovery in the serving PLMN, or if UE intends to use Model B discovery using WLAN-based PC5 and is triggered by the application client to perform a Discoverer Request procedure, the UE shall establish a secure connection to the ProSe Function in the HPLMN and send a Discovery Request (RPAUID, UE Identity, command, Discovery Type, Discovery Model, Application ID, Application Transparent Container, Discovery Entry ID, [PC5_tech]) message. The RPAUID indicates what the UE is interested to announce. The UE Identity is set to IMSI. The command indicates that this is for a ProSe Query operation, i.e. for a Discoverer UE. The Discovery Type is set to "restricted discovery" and the Discovery Model indicates "Model B". The Application ID represents a unique identifier of the UE application that has triggered the transmission of the Discovery Request message. The Discovery Entry ID indicates whether this is a new request. PC5_tech is an optional parameter that indicates the PC5 radio technology (e.g. E-UTRA, WLAN) that UE wishes to use for Model B discovery. PC5_tech may include more than one PC5 radio technology. When this parameter is omitted the intended PC5 radio technology is E-UTRA. This request is always sent to the ProSe Function in HPLMN.
Step 2.
The ProSe Function checks for the authorization of the application represented by the Application ID. If there is no associated UE context, the ProSe Function shall check with HSS the authorisation for discovery and, if necessary, create a new context for this UE that contains the subscription parameters for this UE. The HSS provides the MSISDN of the UE. The HSS also provides the serving PLMN ID of where the UE is registered. When the Discovery Entry ID in the Discovery Request message does not contain a valid value for this UE, the ProSe Function creates a new discovery entry in the UE's context for this request, and returns the corresponding identifier in the Discovery Response message in step 8.
Step 3.a.
The ProSe Function sends an Auth Request (RPAUID, Request Type, Application Level Container) to the ProSe Application Server. The ProSe Function locates the ProSe Application Server based on the Application ID. The Request Type is set to "restricted discovery/query".
Step 3.b.
If, based on the permission setting, the RPAUID is allowed to discover at least one of the Target RPAUID(s) contained in the Application Level Container, the ProSe Application Server returns an Auth Response (PDUID, Response Type, N sets of Target PDUID - Target RPAUID) message. The PDUID corresponds to the RPAUID stored in the ProSe Application Server. The Response Type is set to "restricted discovery/query ack". Each Target ProSe Discovery UE ID is returned with the corresponding Target RPAUID that the RPAUID is allowed to discover. The ProSe Function verifies that the received PDUID belongs to the requesting UE.
 
Step 4 is executed only when the PLMN ID in the Target ProSe Discovery UE ID indicates the HPLMN.
Step 4.
If the PLMN ID in the Target PDUID indicates the HPLMN and at least one of received pair of Target PDUID - Target RPAUID corresponds to a valid ProSe Response Code including a valid PC5 radio technology match as indicated via the PC5_tech parameter in step 1, the ProSe Function locates the Discoveree UE(s) context. The ProSe Function in the HPLMN retrieves the ProSe Query Code and an associated validity timer. The ProSe Query Code is the code used by the ProSe Function to build the Discovery Query Filter of step 4 of clause 5.3.3A.2, such that it can trigger the Discoveree UE to send the response. The ProSe Function allocates a Discovery Response Filter(s) based on the ProSe Response Code. The ProSe Response Code is that allocated to the Discoveree UE in step 4 of clause 5.3.3A.2. The validity timer indicates for how long a ProSe Query Code and ProSe Response Code are going to be valid.
 
Steps 5-7 are executed only when the PLMN ID in the Target ProSe Discovery UE ID indicates a different HPLMN.
Step 5.
If the Discovery Request is authorized, and the PLMN ID in the Target ProSe Discovery UE ID indicates a different PLMN, the ProSe Function contacts the ProSe Function of the indicated PLMN(s) to obtain the necessary information with a Discovery Request (Restricted ProSe App User ID, UE Identity, Target ProSe Discovery UE ID, Application ID, Target Restricted ProSe App User ID, Discovery Entry ID, [PC5_tech]). If the ProSe Function in other PLMN receives the same Discovery Entry ID in a subsequent Discovery Request message, it updates the discoverer UE's corresponding discovery entry with the received corresponding parameters. The request may also include the PC5_tech parameter if it was provided by the UE in step 1. When this parameter is omitted the intended PC5 radio technology is E-UTRA.
Step 6.a.
Optionally, the ProSe Function in the other PLMN sends an Auth Request (RPAUID, Request Type, Target RPAUID) to the Application Server indicated by the Application ID. The request type is set to "restricted discovery/query".
Step 6.b.
If, based on the permission setting, the RPAUID is allowed to discover at least one of the Target RPAUID(s), the ProSe Application Server returns an Auth Response (PDUID, response type, Target PDUID) message. The PDUID corresponds to the RPAUID stored in the ProSe Application Server. The response type is set to "restricted discovery/query ack". The ProSe Function in the other PLMN verifies that the received PDUID belongs to the UE to be discovered.
Step 7.
Based on the Target ProSe Discovery UE ID, Application ID, and Target Restricted ProSe App User ID, the ProSe Function locates the Discoveree UE(s) context, and responds with a Discovery Response (ProSe Query Code(s), ProSe Response Code, validity timer, [PC5_tech]). The ProSe Query Code is the code used by the ProSe Function to build the Discovery Query Filter of step 4 of clause 5.3.3A.2, such that it can trigger the Discoveree UE to send the response. The ProSe Response Code is that allocated to the Discoveree UE in step 4 of clause 5.3.3A.2. The validity timer indicates for how long a ProSe Query Code and ProSe Response Code are going to be valid. The optional PC5_tech parameter indicates the PC5 radio technology(ies) that is/are authorized to be used for the assigned ProSe Query Code. When this parameter is omitted, the authorized PC5 radio technology is E-UTRA.
Step 8.
The ProSe Function in the HPLMN shall respond with a Discovery Response (Discovery Model, ProSe Query Code(s), Discovery Response Filter(s) validity timer, [PC5_tech]) message. The Discovery Model indicates the Model B is used. Multiple Discovery Response Filters may be returned. The Discovery Response Filter is generated by the ProSe Function based on the ProSe Response Code of step 4 or received in step 7. The ProSe Query Code is that of step 4 or is received in step 7. The validity timer indicates for how long a ProSe Query Code and corresponding Discovery Response Filter(s) are going to be valid. When the validity timer expires the UE needs to UE needs to initiate a new Discoverer Request procedure. The optional PC5_tech parameter indicates the PC5 radio technology(ies) that is/are authorized to be used for the assigned ProSe Query Code. When this parameter is omitted, the authorized PC5 radio technology is E-UTRA.
Step 9.
The UE may then obtain the radio resources to announce the ProSe Query Code, as authorised and configured by E-UTRAN for ProSe as defined in RAN specifications, or uses WLAN or both.
If the validity timer associated with a ProSe Query Code expires (because the UE has not refreshed the corresponding Discovery Request within the duration of the validity timer), then the ProSe Function removes the entry related to that ProSe Query Code from the UE context.
Up

5.3.3A.5  Discoverer request (roaming/inter-PLMN transmission) - restricted discoveryWord‑p. 78
(not reproduced yet)
Figure 5.3.3A.5A-1: Discoverer UE procedures for Model B restricted discovery (roaming)
Up
The UE is only allowed to announce in the carrier frequency signalled from serving PLMN. When inter-PLMN discovery transmission is supported, the carrier frequency may be operated by Local PLMN.
Step 0.
In this step, the application client in the UE retrieves its own PDUID and provides it to the ProSe Application Server. The ProSe Application Server allocates a Restricted ProSe Application User ID (RPAUID) for that PDUID, stores the binding between the PDUID and the RPAUID and returns the RPAUID to the application client in the UE. The application client in the UE stores the binding between the PDUID and its own RPAUID. When the application client in the UE intends to query a UE of other users (e.g. friends in the application), it obtains the RPAUID of those users (Target RPAUIDs) from the ProSe Application Server and triggers the UE to perform the ProSe query procedure, providing its own RPAUID and the Target RPAUIDs. The Target RPAUIDs of the UEs to be queried are passed in an Application Level Container.
Step 1.
If the Discoverer UE is authorised to use Model B discovery in the PLMN operating the carrier frequency signalled by the serving PLMN, or if UE intends to use Model B discovery using WLAN-based PC5 and is triggered by the application client to perform a Discoverer Request procedure, the UE shall establish a secure connection to the ProSe Function in the HPLMN and send a Discovery Request (RPAUID, UE Identity, command, Discovery Type, Discovery Model, Application ID, Application Transparent Container, Discovery Entry ID, [Announcing PLMN ID], [PC5_tech]) message. The RPAUID indicates what the UE is interested to announce. The UE Identity is set to IMSI. The command indicates that this is for a ProSe Query operation, i.e. for a Discoverer UE. The Discovery Type is set to "restricted discovery" and the Discovery Model indicates "Model B". The Application ID represents a unique identifier of the UE application that has triggered the transmission of the Discovery Request message. The Discovery Entry ID indicates whether this is a new request. If inter-PLMN ProSe discovery transmission is supported, and the serving PLMN signalled carrier frequency is not operated by HPLMN or VPLMN, the UE shall include the PLMN ID of that carrier frequency in the Announcing PLMN ID. PC5_tech is an optional parameter that indicates the PC5 radio technology (e.g. E-UTRA, WLAN) that UE wishes to use for Model B discovery. PC5_tech may include more than one PC5 radio technology. When this parameter is omitted the intended PC5 radio technology is E-UTRA. This request is always sent to the ProSe Function in HPLMN.
Step 2.
The ProSe Function checks for the authorization of the application represented by the Application ID. If there is no associated UE context, the ProSe Function shall check with HSS the authorisation for discovery and, if necessary, create a new context for this UE that contains the subscription parameters for this UE. The HSS provides the MSISDN of the UE. The HSS also provides the serving PLMN ID of where the UE is registered. When the Discovery Entry ID in the Discovery Request message does not contain a valid value for this UE, the ProSe Function creates a new discovery entry in the UE's context for this request, and returns the corresponding identifier in the Discovery Response message in step 10.
Step 3.a.
The ProSe Function sends an Auth Request (RPAUID, Request Type, Application Level Container) to the ProSe Application Server. The ProSe Function locates the ProSe Application Server based on the Application ID. The Request Type is set to "restricted discovery/query".
Step 3.b.
If, based on the permission setting, the RPAUID is allowed to discover at least one of the Target RPAUID(s) contained in the Application Level Container, the ProSe Application Server returns an Auth Response (PDUID, Response Type, N sets of Target PDUID - Target RPAUID) message. The PDUID corresponds to the RPAUID stored in the ProSe Application Server. The Response Type is set to "restricted discovery/query ack". Each Target ProSe Discovery UE ID is returned with the corresponding Target RPAUID that the RPAUID is allowed to discover. The ProSe Function verifies that the received PDUID belongs to the requesting UE.
 
Step 4 is executed only when the PLMN ID in the Target ProSe Discovery UE ID indicates the HPLMN.
Step 4.
If the PLMN ID in the Target PDUID indicates the HPLMN and at least one of received pair of Target PDUID - Target RPAUID corresponds to a valid ProSe Response Code including a valid PC5 radio technology match as indicated via the PC5_tech parameter in step 1, the ProSe Function locates the Discoveree UE(s) context. The ProSe Function in the HPLMN retrieves the ProSe Query Code and an associated validity timer. The ProSe Query Code is the code used by the ProSe Function to build the Discovery Query Filter of step 4 of clause 5.3.3A.3, such that it can trigger the Discoveree UE to send the response. The ProSe Function allocates a Discovery Response Filter(s) based on the ProSe Response Code. The ProSe Response Code is that allocated to the Discoveree UE in step 4 of clause 5.3.3A.3. The validity timer indicates for how long a ProSe Query Code and ProSe Response Code are going to be valid.
 
Steps 5-7 are executed only when the PLMN ID in the Target ProSe Discovery UE ID indicates a different HPLMN.
Step 5.
If the Discovery Request is authorized, and the PLMN ID in the Target ProSe Discovery UE ID indicates a different PLMN, the ProSe Function contacts the ProSe Function of the indicated PLMN(s) to obtain the necessary information with a Discovery Request (Restricted ProSe App User ID, UE Identity, Target ProSe Discovery UE ID, Application ID, Target Restricted ProSe App User ID, Discovery Entry ID, [PC5_tech]). If the ProSe Function in other PLMN receives the same Discovery Entry ID in a subsequent Discovery Request message, it updates the discoverer UE's corresponding discovery entry with the received corresponding parameters. The request may also include the PC5_tech parameter if it was provided by the UE in step 1. When this parameter is omitted the intended PC5 radio technology is E-UTRA.
Step 6.a.
Optionally, the ProSe Function in the other PLMN sends an Auth Request (RPAUID, Request Type, Target RPAUID) to the ProSe Application Server indicated by the Application ID. The Request Type is set to "restricted discovery/query".
Step 6.b.
If, based on the permission setting, the RPAUID is allowed to discover at least one of the Target RPAUID(s), the ProSe Application Server returns an Auth Response (PDUID, Response Type, Target PDUID) message. The PDUID corresponds to the RPAUID stored in the ProSe Application Server. The Response Type is set to "restricted discovery/query ack". The ProSe Function in the other PLMN verifies that the received PDUID belongs to the UE to be discovered.
Step 7.
Based on the Target ProSe Discovery UE ID, Application ID, and Target Restricted ProSe App User ID, the ProSe Function locates the Discoveree UE(s) context, and responds with a Discovery Response (ProSe Query Code(s), ProSe Response Code, validity timer, [PC5_tech]). The ProSe Query Code is the code used by the ProSe Function to build the Discovery Query Filter of step 4 of clause 5.3.3A.3, such that it can trigger the Discoveree UE to send the response. The ProSe Response Code is that allocated to the Discoveree UE in step 4 of clause 5.3.3A.3. The validity timer indicates for how long a ProSe Query Code and ProSe Response Code are going to be valid. The optional PC5_tech parameter indicates the PC5 radio technology(ies) that is/are authorized to be used for the assigned ProSe Query Code. When this parameter is omitted, the authorized PC5 radio technology is E-UTRA.
Step 8.
The ProSe Function in the HPLMN shall inform the ProSe Function in VPLMN or Local PLMN if Announcing PLMN ID is included in step 1 with the Announce Authorisation (Restricted ProSe Application User ID, Application ID, ProSe Query Code(s), validity timer, UE Identity, Discovery Entry ID, [PC5_tech]) message. The Restricted ProSe Application User ID corresponds to the request from the UE, whereas the ProSe Query Code is that of step 4 or is obtained in step 7. The request also includes the UE identity information e.g. IMSI or MSISDN in order to allow the ProSe Function in VPLMN or Local PLMN to perform charging. The validity timer indicates for how long this ProSe Query Code is going to be valid. If the ProSe Function in VPLMN or Local PLMN receives the same Discovery Entry ID in a subsequent Announce Authorization message, it updates the discoverer UE's corresponding discovery entry replacing the existing ProSe Query Code(s) and validity timer with the last received ones. The request may also include the PC5_tech parameter if it was provided by the UE in step 1. When this parameter is omitted the intended PC5 radio technology is E-UTRA.
Step 9.
The ProSe Function in VPLMN or Local PLMN authorizes the UE to perform ProSe Direct Discovery announcing.
Step 10.
The ProSe Function in the HPLMN shall respond with a Discovery Response (Discovery Model, ProSe Query Code(s), Discovery Response Filter(s) validity timer, [PC5_tech]) message. The Discovery Model indicates the Model B is used. Multiple Discovery Response Filters may be returned. The Discovery Response Filter is generated by the ProSe Function based on the ProSe Response Code of step 4 or received in step 7. The ProSe Query Code is that of step 4 or is received in step 7. The validity timer indicates for how long a ProSe Query Code and the corresponding Discovery Response Filter(s) are going to be valid. When the validity timer expires the UE needs to initiate a new Discoverer Request procedure. The optional PC5_tech parameter indicates the PC5 radio technology(ies) that is/are authorized to be used for the assigned ProSe Query Code. When this parameter is omitted, the authorized PC5 radio technology is E-UTRA.
Step 11.
The UE may then obtain the radio resources to announce the ProSe Query Code, as authorised and configured by E-UTRAN for ProSe as defined in RAN specifications or uses WLAN, or both.
If the validity timer associated with a ProSe Query Code expires (because the UE has not refreshed the corresponding Discovery Request within the duration of the validity timer), then the ProSe Function removes the entry related to that ProSe Query Code from the UE context.
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